: Scaling kayaks up or down (length for example) doesn't have a linear
: relationship to either the displacement or the wetted surface.
: These ballpark figures come from proportional longitudinal scaling of kayak
: lengths (not just bringing the two middle stations together for instance)
: while keeping the draft and BWL same (well, +- 1/4"). You can use
: these figures (within reason) to extrapolate the changes in displacement.

Hi Vac

I think there are a few things I'm not quite getting(no big surprise there).

Keeping the draft and BWL the same means all the sections are the same and only the proportional length changes. If I relate it to something I can understand - say the block coefficient (simple lxwxh of max dimensions only) with only the length changing, does the block coefficent go down faster than the proportional lesser length?(like the block goes down linearly - why not the yak?) And vice versa - does it reach 1 faster than the increase in length? Like a double curve? There's some subtlety here I don't get.

If the first question was 95% proportional length & width & ht and therefore draft(all things being proportional), I would have expected it to be as the other stated (.95 cubed). The nonlinearity(or square or cube depending on no. of variables changed), I would expect only if the draft is not varied proportionally with the varying ht.

: Also,the thing to look at is the designed displacement and not the maximum
: capacity which is pretty much meaningless. At 300lb load you might as well
: be riding a sinking log.

If talking about a real log - probably would displace 1000's of lbs, but the picture analogy is pretty good. For many yaks max capacity is of paramount importance. And for many also a 'sorta total volume distribution prismatic coefficient' is of big interest(and balance volume too). Like playboats (for cartwheels-want it low to slice) and squirt boats(for mysteries and mucho other). If you're talking about 300lb additional total (3-d complete) displacement, you're talking close to my beater. If max total, squirts are somewhere in between the 300# and me(530#). (not quite sure where)

-mick